Introduction
I have long dreamed of having a custom A/V room, designed from the ground up in order to obtain optimum performance from my audio/video system. The design would address everything from room acoustics to EMI noise isolation. When it comes to AC power, if cost was no object, I would have separate dedicated transformers on the power pole for each electronic component. Although totally impractical, this would be the best way to keep noise generated by other electronic devices, such as computers, water heaters, refrigerators and even other audio components, from infiltrating my beloved sound system.

A more practical approach would be to use power filters like the new Transparent PowerIsolator IV, which provides both noise filtering and surge protection. On the surface, this may not sound so impressive, since you can purchase a device at your local hardware store that does this for around three dollars. However, filtering power from the AC lines without negative effects on sound or picture quality is extraordinarily tricky and rarely accomplished without sonic downsides.

The PowerIsolator IV measures eighteen-and-seven-eighths inches wide, five-and-one-eighth inches tall and nine inches deep, weighs 17 pounds, and sells for $1,895. The front panel has the Transparent nameplate and a single LED that lights up only when there is a problem. The unit is designed to be rack-mountable or to sit on an equipment shelf. The enclosure has a black anodized machined aluminum faceplate and a black powder-coated steel shell. The unit feels solid and looks well built. It has four hubell hospital grade 5-15 outlets for up to four different components. Transparent recommends one PI IV for each component for optimum performance. However, other configurations, such as one unit for analog components and one for digital components, are said to achieve very good performance.

The Technology
The obvious goal of a power filter is to remove noise from the power
line in hopes of lowering the noise floor in a piece of electronics.
Most filter devices on the market use inline chokes or capacitors,
which create a phase shift between the voltage and current. This can
cause the current to lead or lag the voltage. According to Transparent,
this causes a small drop in power supply performance, which can be
heard as added harshness in some cases, or a dull lifeless sound in
others.

Power correction is not a new idea, as there are many different
products, each with different design philosophies. Another popular
approach for improved power is power regeneration. This approach uses a
circuit to convert the AC power to DC and back to AC again. This is
like adding an amplifier to drive your amplifier. This is not what
Transparent does to clean up your power.

The PI IV design uses no components in the power path in order to avoid
any possibility of limiting the current. The noise filter is designed
to filter everything from 1 KHz and above, with the minus three dB
point at 2 KHz. The all-passive filter in the PI IV is designed
specifically to avoid any phase shift at 60 Hz. Transparent claims that
this is key to providing noise filtering with no negative effects. When
it comes to surge protection, it’s pretty easy to understand the
importance of protecting your investments, yet once again, providing
surge protection without affecting sound or picture quality can be
difficult. To top that off, most surge suppressors use MOVs that cannot
react fast enough to protect the upstream equipment from damage in the
most extreme cases. The PI IV employs a hybrid circuit, which utilizes
avalanche diodes. Avalanche diodes represent state of the art
performance and cost in surge protection. These devices react in
picoseconds where as MOVs react in nanoseconds. The PI IV’s surge
protection circuit does not allow any voltage above 200 volts to pass
into the connected equipment and theoretically can protect against
extreme cases, such as lightning strike voltage surges. Transparent
backs up this claim with a five-year connected equipment warranty.

Movies and Music
Set-up is as simple as plugging in a power cord. Initially, I connected
only my Plus Piano HE -3200 to see what effect filtered power would
have on my picture. I put in “Scooby-Doo” (Warner Home Video) and was
amazed by the obvious changes that occurred. During the scene where
Scooby and Shaggy are trapped by the monsters, I saw an obvious
improvement in the colors, which all appeared brighter and better
defined. In particular, the fur on Scooby looked more real. I could see
variations in the brown that were not noticeable before. Additionally,
I could see the shadowing around the fur and noticed subtle movements
in the fur as Scooby and Shaggy discussed their impending doom. The
PowerIsolator provided better edges to the images, making them look
more three-dimensional.

I then disconnected the projector and connected a Linn Twin amplifier
and Conrad Johnson 16LS preamplifier to the PI IV. Although I have
always been a little skeptical about how much difference a power filter
can make, I was amazed at the improvements that I heard. During “Tom
Thumb,” the third track on Bob Belden’s Shades of Blue (Blue Note), I
immediately noticed the increased separation in the instruments. The
bass line was more clearly defined and I could hear more of the
subtleties. The cymbals had an increased presence in my room and gave
me a greater sense of being present at the live performance. During
track five “Siete Ocho,” I was astonished by how real the cymbals
sounded. I could hear more of the inner detail as the cymbal resonated
and visualize the resonance circling the cymbal as it decayed naturally
into darkness. The transient attacks that occurred when the drumstick
hit the rim of the drum seemed more believable than I have ever heard
in my system. On Track Seven, “Hum Drum Blues,” Holly Cole’s voice
floated beautifully in the center of the stage. The saxophone frankly
blew me away. It appeared out of darkness almost as if it were in the
room. I could hear the air as it left the horn. The subtlest sounds in
the body of the instrument were naturally audible as never before and
translated into a more believable presentation.

“Before You Accuse Me” on Eric Clapton’s Unplugged CD (Reprise) drew me
in beautifully. I have heard this disc many times and have always felt
like the stage was little compressed and the highs been on the edgy
side. With the PI IV, most of the maladies were gone. Eric Clapton’s
voice seemed more natural than ever, with very little edginess. The
stage seemed larger, with better separation between the instruments. On
track Three, “Hey Hey,” I was mesmerized by the melody created by the
dueling guitars. I normally skip this track, but ended up listening to
it from beginning to end a couple of times. I was entranced by the
detail in the guitars. Never before had the sound of the strings
snapping off of Eric Clapton’s fingers been so clear.

Aretha Franklin’s I Never Loved a Man the Way I Love You (Mobile
Fidelity Sound Lab) is one of my favorite classic R&B CDs. This is
an older album from 1967, with some obvious recording flaws. For this
reason, I was surprised at the size of the stage that I was now
getting. The separation between the instruments was now better than I
would ever have expected. On Track Five, “Don’t Let Me Lose This
Dream,” I had instruments well outside my speakers and the walls of my
room started to disappear. There was almost no blending or smearing of
instruments.

On “Hells Bells,” the first track on AC/DC’s Back in Black CD (ATCO
Records), the large bell in the intro rang beautifully and filled the
room with sound. The guitar appeared clearly set back on the right side
of the stage. When the kick drum and bass came up, the whole stage was
set in front of me. I found the volume creeping up and staying up. I
cannot typically listen at these levels for extended periods, but with
the PI IV installed, much of the harshness was removed and the detail
exposed.

I had a great time cycling through the Jazz Masters Volume Two set (Da
Music) that I just picked up. Stephane Grappelli and Barney Kessel play
“It Don’t Mean a Thing If It Ain’t Got That Swing” better than I have
ever heard it before. Grappelli did things with his violin that I
didn’t think were possible, and Kessel is no less amazing on guitar.
The stage is set with Kessel on the left and Grappelli on the right.
With this track, the walls in my room vanished and I was transported
out of my listening room to the original event.

AudioRevolution.com editor Bryan Southard and I have been friends for
many years and we live relatively close to one another in Northern
California. We have traveled far and auditioned many products together
over the years. As Southard has reviewed most of the higher-profile A/C
power products for Audiorevolution.com over the years, I felt it
appropriate to bring the Transparent PowerIsolator IV to his reference
system for a second opinion and further testing. We made several direct
comparisons to other A/C power units in his system and his opinion
wholeheartedly echoed mine. It was his opinion that among all of the
power products that he has reviewed, no other A/C product drew greater
separation between the instruments and the surrounding air than the
Transparent PI IV. I felt that he was initially skeptical about this
product, because the word “filtering” had conjured up thoughts of poor
filter-based products of the past. In direct comparison, Southard felt
that the regeneration devices that he had reviewed in the past had done
very positive things for the instruments themselves, but felt that they
appeared to do little to the black areas between the instruments and
rather fooled the ear into believing that these spaces were quiet. It
was our opinion that the Transparent PI IV had significantly better
vocal and instrumental textures and provided a more relaxed and
detailed presentation, allowing us to experience more of the physical
event. It was Southard’s opinion that the PI IV was the best A/C
product that he had heard to date and one that he personally recommends
at the highest level.

The Downside
The Transparent PowerIsolator IV is a tremendous value when compared to
other power-related products. It performs exceptionally and will make
“sheer” magic. However, at $1,895 each and with the potential need for
more than one, this product is best suited for A/V systems that are
already high performers seeking additional performance. Due to cost, I
would only recommend the PI IV for A/V systems costing $8,000 and up.

Conclusion
If you like the sound of your system now, wait until you hear how much
better it can sound with cleaner power. For those skeptics out there,
you don’t know what you have been missing. I was nothing short of
amazed at how much of an improvement that the Transparent PowerIsolator
IV made in my system and Southard’s alike.

I have some great equipment and had started to wonder if it could get
much better. The PowerIsolator IV has opened my mind to the
possibilities. I can only imagine what would happen if I had all of
Transparent’s power cords and four or five of the PI IVs. When I tell
people how expensive my sound system is, some ask why I don’t just sell
all of my equipment and spend the money going to live performances. All
I can say to that is that a good music playback system can be like a
time machine. How much would you pay to be transported back in time to
your favorite musician’s best performance, and have the best seat in
the house? The Transparent PowerIsolator IV will take you that much
closer to the live event. In the world of A/C optimization, it is
unequaled at any cost.

Transparent offers less expensive units for smaller system priced from $575.